Ignition system with stabilizer



July 4, 1939- D. w. RANDOLPH E-r Al. 2,164,472

IGNITION SYSTEM WITH STABILIZER Filed Oct. 2l, 1936 5 Sheets-Sheet 1 dl- *1r- MNHN MAG.

July 4, 1939 D. w. RANDOLPH ET AL 2,154,472

IGNITION SYSTEM WITH STABILIZER July 4, 1939- D. w. RANDOLPH ET AL 2,164,472

IGNITION SYSTEM WITH STABILIZER Filed oct. 21, 193e s sheets-sheet s Patented July 4, 1939 UNITED STATES PATENT OFFICE 2,164,472 IGNITION SYSTEM WITH STABILIZER Donald W. Randolph and Ralph H. Mitchel,

Flint, Mich., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware This is an improvement in ignition circuits of the type described and claimed in Patent No. 2,071,573, granted to Randolph and Rabezzana on February 23, 1937.

In such circuits the electrical energy generated by a magneto or other electrical generator is stored in a condenser until its voltage reaches the breakdown voltage of a suitable electrical valve such as a gaseous discharge tube having spaced electrodes in series with the condenser. When therequired voltage is attained a discharge takes place between the electrodes causing a surge of current which ows from the condenser through the tube and through the primary of a transformer the secondary of which is in series with the ignition devices, such as the 'usual spark plugs. A distributor is provided in series with the secondary to direct the discharge to the plugs in proper sequence. y It has been found that timing of the spark at the higher speeds may be very considerably improved by introducing a stabilizer between the magneto and the condenser. The stabilizer preferably takes the form of an auto-transformer which steps down the voltage supplied to the condenser by the magneto. When such a stabilizer is employed the sparking is much more regular and the natural retardation of the spark at high speeds is considerably reduced. The action of the stabilizer may be explained on the theory that the condenser retains a charge between -sparks and the stabilizer serves as a means to discharge the condenser so' that recharging will begin with the condenser always at zero, or approximately zero, potential.

Since the stabilizing transformer reduces the voltage applied to the condenser, when such a coil is used the magneto must be driven at higher speed in order to generate suflicient voltage to cause discharge through the valve. Since it is essential that the ignitionsystem function satisfactorily when the engine is being turned over slowly by the starting motor, as in wintertime when the oil is thick and the battery low, the 'stabilizer is preferably not connected to the circuit until the engine has beenv started and has reached a running speed. This may be done very simply by having the stabilizer normally 50 disconnected by means of a centrifugal switch which closes automatically when the engine speed increases and so brings the stabilizer into operation. Other methods of accomplishing the same result are described hereinafter. In the drawings:

Figure .1 is a diagrammatic view of one form of the improved ignition circuit.

Figures and 3 are diagrammatic views showing modifications.

Figure 4 is a view corresponding to Figure 1 5 but showing a centrifugal switch controlling the stabilizing coil. l

Figure 5 is a plan view of the centrifugal switch with the parts at'rest.

Figure 6 is a similarview showing the position 10 the switch assumes under the action of centrifugal force.

Figure 7 is a section on line 1-1 of Figure 5.

Figure 8 is a section on line 8-8 of Figure 6.

Figure 9 is a view corresponding to Figure 1 l5 showing a starter pedalV operated switch controlling the stabilizing coil, with a resistance in series.

Figure 10 is a veiw showing the switch of Figure 9.

Figure 11 is a longitudinal view through the 20 switch of Figure 10.

Figure 12 is a section on line I2-l 2 of Figure 11.

Figure 13 is a .View corresponding to Figure 4 showing the combination of the stabilizing coil controls of Figures 4 and 9. 25

The circuit shown in Figure l is of the general type disclosed and claimed in the above mentioned Randolph and Rabezzana application. The magneto, marked Mag, preferably consists of a rotating magnet having as many poles as the' 30 engine has cylinders, and a stationary field having a winding for each pole, the windings being arranged in series. Current from the magneto is supplied to a step down auto-transformer A arranged to supply energy to condenser C. When 35 the charge on the condenser C reaches the required voltage it discharges through electric valve V and the primary winding of step up transformer T. The secondary winding of the transformer then supplies a surge of current to the spark 40 plug S to which energy is directed by the distributor D. The drawings show the various circuits completed by a common conductor. In practice this conductor is usually a common ground. The electric valve preferably takes the form of a two electrode gaseous discharge tube such as is described and claimed in the prior application of Duifendack, Randolph and Wolfe, Serial No. 716,972; filed March 23, 1934. The described circuit functions to produce a heavy surge of current (which may have an instantaneous value of from 25 to 50 amperes) through the primary of the transformer upon breakdownof the tube, and this produces a good spark or rather a series of sparks at the plug,A the series of sparks speeds as low as are obtainable with the autof being due to the oscillating character of the discharge.

While as described in the prior Randolph and Rabezzana application S. N. '727,888 the circuit is effective with the condenser C connected directly across the magneto terminals, the auto-g transformer A acts as lan effective stabilizing device overcoming irregularity of timing of the spark which occurs at the higher magneto speeds, for example, speeds in excess of 400 R. P. M. While the stabilizer does not completely overcome irregularity in sparking at the higher speeds, it holds it within suiciently narrow limits so as to be practically unobjectionable. The autotransformer also reduces the retarding of the spark which increases with the increase in magneto speed. However, for best results it will be found desirable to provide some form of automatic spark advance such as that disclosed in said Rabzzana and Randolph Patent No. 2,071,573.

In Figure 2 there is shown a modified form of stabilizing means in which theI auto-transformer is replaced by a conventional step-down transformer T with two windings. effect stabilization of the spark timing, it is not as desirable because the transformer must contain a large volume of iron to obtain starting transformer. In this Figure as well as in Figures 3, 4, 9 and 13, the distributor is omitted and a spark gap is indicated diagrammatically at G to simplify the showing.

The circuit shown in Figure 3 is the same as that shown in Figure 1 except that the autotransformer is replaced by a resistance coil R connected as a potentiometer across the magneto.

The effect of the stabilizing means in all of the above described circuits is to raise the starting speed. This\is.undesirable for it is., necessary to be able to start the engine at ver'yflow speeds as in winter-time when the starting motor barely turns the engine over. Provision is, therefore, preferably made to cut out the stabilizing means at starting. Thesubsequent figures show arrangements for accomplishing this in connection with the' type of circuit shown in Figure 1 employing a stabilizing means in( the form of an auto-transformer, although .these same arrangements are equally applicable'to the forms of circuits shown in Figures 2 and 3. The simplest arrangement'is that'shown in Figure 4 in which the circuit through the auto-transformer is norally open but is completed through centrifugal switch I0 when the engine attains sufficient speed. Centrifugal switch I0 may be of the construction shown in Figures 5 to 8. Here I2 indicates a shaft driven by the engine, preferably the magneto rotor shaft. I4 indicates weights pivoted to bracket I6 secured to the shaft. Weights I4 are connected by link I6 pivoted to one of them and having pin and slot connectionwith the other, and by spring I9 normally holding the weights close to the shaft. 2li indicates a switch arm pivoted to a suitable fpart of the stationary switch housing and carrying contact member 22 adapted to complete contact between the switch blades 24. 26 indicates stops hunting the amount of swing of arm 2li.v Compression spring 28 holds the switch arm in either of its extreme positions. Switch arm 20 carries cams 30 adapted to be engaged by lug 32 .carried by one of the weights I4 during the rotation thereof.

With the switch parts in the position shown in Figure 5 switch arm 20 will occupy the posi- While this will tion shown. As the speed of the shaft increases 'Y theweights I4 are swung outwardly by centrifugal force until pin 32 strikes the outer cam 30 whereupon arm 20 is swung over to the position shown in Figure 6 in which member 22 reverse action takes place upon decreasing speed,`

the stabilizer being cut out of the circuit by the centrifugal switch at the said predetermined speed.

In the arrangement shown inA Figure 9, the switch 36 is connected as shown in Figures 19 to 12 so that it is open as long as the starterpedal is depressed, thereby cutting out the stabilizing coil. Upon release of the starter pedal or other starting switch, the switch 36 is automatically closed by the spring 38, bringing the stabilizing coil into, operation. The resistance 40 increases the impedance of the auto-transformer and ixn.

proves the low speed performance, although it tends to produce greater irregularityof sparking at higher speeds. sistance 40, an' auto-transformer of higher impedance may be employed.

The details of the starting switch arrangement illustrated diagrammatically in Figure' 9 are shown in Figures 10 to 12. Switch 36 preferably takes the form of blades 44- normally bridged by contact 46 carried by and insulated from switch arm 48 which is urged Instead of employing the reto circuit closing position by the torsion spring 38. One end of the arml 4,8 is slidably connected as by coil spring `50 to starter switch operating lever 52 which is adapted to be actuated by the starter pedal 54, and in turn actuates the plunger 56 of the starter switch. Obviously, upon depression of the starter pedal or button 54 the arm 52 is swung to position to close the starter switch and at the same time a pull is applied to spring 50 causing arm 46 to be moved to the dotted line position shown in `Figure 11 opening the circuit at the blades 44, and thus disconnecting the stabilizer coil as shown in Figure 9.

The arrangement shown in Figure 13 vis a combination of the stabilizing coil controls of Figures 4 and 9. With this arrangement the switch 36 is maintained open as long as the ,starter pedal ls depressed and the centrifugal switch I0 Ais maintained open until the enginereaches a suitable speed. Hence on starting the stabilizing coil is disconnected from the circuit. Upon the release of the starter switch, switch 36 is'closed whereupon the stabilizing coil is brought into action, but the resistance 40 cuts down .the effect of the coil at low speeds. When the engine has attained a desired running speed on the order of 400 or 500 R. P. M.' centrifugal switch I0 closes shunting out the resistance 40 and giving regularity of firing throughout the remainder of the speed range. In the design of the auto-transformer it is, of course, apparent that the higher the step-down ratio the higher the speed at which the magneto must be driven to attain the sparking voltage. Hence from this consideration a low step-down ratio would be desirable. However, the stabilizing f Cir property of the transformer increases with the transformer ratio. Hence the final design of the transformer must embody a compromise between these two considerations, "and we have found it desirable in the case of an ignition system of this type equipped with electric valves breaking down at from 145 to 150 volts D. C., to employ a stepdown transformer of a` ratio of approximately 2151. In the design f the auto-transformer care is to be used in the amount of iron employed. Too much iron gives lower starting speed but with lack of stability at higher magneto speeds, while too little iron gives good stability but at the sacrifice of higher starting speed. Y

With the stabilizer cut out of the circuit by any of the means described it has proven possible to readily start the engine at the lowest cranking speeds found necessary in practice. With the stabilizer in circuit the regularity of sparking and the timing of thespark is suiiciently regular to provide satisfactory operation at all speeds throughout the driving range.

With the described arrangement the variation in sparking may be held within feasible limits, for example, on the order of plus or minus 1. The natural characteristic of the magneto which causes the spark to become increasingly retarded as the speed increases, makes it necessary to provide for automatic spark advance with the increase in engine speed. This may be done by known methods such as are disclosed in the said Randolph and Rabezzana Patent No. 2,071,573, in which the magneto stator is moved in a direction to produce spark advance by the combined action of engine suction and Water or oil pressure acting on suitable diaphragms connected to the stator.

The ignition system described possesses the important advantages of firing satisfactorily even though the spark plugs be fouled by carbon or the like, and of more satisfactory ignition at high engine speeds, for the voltage applied at the gap does not decrease with increased speed as is the tendency in the case of battery ignition systems. The system is likewise characterized by lack of parts requiring replacement since the ignition tubes and other parts have substantially indefinite life.

We claim: l

1. In a high frequency impulse circuit the combination of an alternating current generator, stabiliaing means connected across the generator, a condenser in Vparallel with the stabilizing means, and a discharge circuit for the condenser comprising an electric valve adapted to break down upon application of a predetermined voltage.

2. In the combination as defined in claim 1, a work circuit coupled to said condenser discharge circuit.

3. In the combination as defined in claim 1, the stabilizing means consisting of a step-down transformer.

4. In the combination as defined in claim 1, the stabilizing means consisting of a step-down autotransformer.

5. In the combination as defined in claim 1, the stabilizing means consisting of a potentiometer.

6. In the combination as dened in claim 1, speedcontrolled means for stabilizing means when the generator speed reaches a predetermined minimum.

7. In an ignition system the combination of a generator, stabilizing vmeans in parallel with the generator, a condenser connected across the stabilizing means,` and a discharge circuit for the disconnecting the condenser comprising an electric valve, and an ignition device connected to said discharge circuit so as to receive energy therefrom upon break-down of the valve.

8. In an ignition system the combination of a generator. a step-down transformer connected across the generator, a condenser connected across the secondary of the transformer, and a discharge circuit for the condenser comprising an electric valve, and an ignition device connected to said discharge circuit so as to receive energy therefrom.

9. In an ignition system the combination of a generator, a step-down transformer connected across the generator, a condenser connected across the secondary of the transformer, and a discharge circuit for the condenser comprising an electric valve and an ignition device inductively coupled to said discharge circuit.

10. In an ignition system the combination of a generator, a step-down transformer connected across the generator, a condenser connected across the secondary of the transformer, and a I discharge circuit for the condenser comprising an electric valve and the primary of a step-up transformer, and an ignition device inseries with the secondary of said step-up transformer.

11. In an ignition system the combination of a generator, a step-down transformer connected across the generator, a condenser connected across the secondary of the transformer, and a discharge circuit for the condenser comprising an electric valve and the primary of a step-up transformer, a plurality of ignition devices, and a distributor for connecting said ignition devices in succession with the secondary of said step-up transformer.

12. In an ignition system the combination of an alternating current generator, a step-down auto-transformer connected across the generator, acondenser in parallel with the secondary of said transformer, an electric Valve and the pri-4 mary of a step-up transformer in series with the condenser, an ignition device, and means for connecting the ignition device to the secondary of said step-up transformer so as to receive energy therefrom.

13. In an ignition system the combination of an alternating current generator, a step-down auto-transformer connected across the generator, a condenser in parallel with the secondary of said transformer, a gaseous discharge tube having spaced electrodes in series with the condenser and with the primary of a step-up transformer, an ignition device, and means for periodically connecting the ignition device in series with the secondary of said step-up transformer.

14. In an ignition system the combination of a generator, an ignition device, means `for supplying energy from the generator to the ignition device including spark stabilizing means adapted to lbe connected across the generator but normally disconnected therefrom, means for completing the connection of the stabilizing means to the generator including a resistance, and means for cutting out said resistance.

15. In the combination as defined in claim 14,

and means for actuating said last named means.

in sequence.

16. The combination of an internal combustion engine, a starter therefor, a switch controlling the starter, an ignition system for the engine comprising an alternating current generator, an ignition device, a circuit for supplying energy from the generator to the'ignition device, spark stabilizing means connected across the generator in series with an impedance, means operated by actuation of the starter switch for disconnecting the stabilizing means from the ignition circuit, and means operable by the engine upon attainment of a predetermined speed for cutting out said impedance.

1'7. The combination of an internal combustion engine, a starter therefor, a switch controlling the starter, an ignition system for the engine comprising a generator, an ignition device, means for supplying energy from the generator to the ignition device including spark stabilizing means, an impedance in series with the stabilizing means, and means actuated by operation of the starter switch for disconnecting the stabilizing means and impedance from the circuit.

18. In an ignition system, the combination of a generator, stabilizing means connected across the generator, a condenser connected to the stabilizing means so as to be supplied with energy from the generator, a discharge. circuit for the condenser including means adapted to break down upon application of a predetermined voltage, an ignition device,lmeans for supplying said ignition device with energy from said discharge circuit, and means for temporarily disconnecting the circuit through the stabilizing means.

19. In the combination as defined in claim 18, said last named means being responsive to the speed of the generator.

20. The combination of an internal combustion engine, a starter therefor, a switch controlling the starter, an ignition system for the engine comprising a generator, stabilizing means connected across the generator, a condenser connected t the stabilizing means so` as to be supplied with energy from the generator through the stabilizing means, a discharge circuit for the condenser including means adapted to break down upon application of a predetermined voltage, an ignition device for the engine, means for supplying said ignition device with energy from said discharge circuit, and means actuated by operation of the starter switch for disconnecting the circuitl through the stabilizing means.

21. In an impulse circuit the combination of a generator, stabilizing means connected across the generator, a condenser -connected to the stabilizing means so as to be supplied with energy from the generator, and a discharge circuit for the condenser comprising means adapted to break down upon application o f a predetermined voltage.

22. In an impulse ignition system for variable speed internal combustion engines, means driven by the engine for generating alternating current impulses at a variable frequency determined by the speed of the engine, a stabilizing impedance connected across the generating means, a condenser in parallel with the impedance, and a discharge circuit for the condenser comprising an electric valve adapted to break down when the applied impulse attains a predetermined voltage, and an ignition device connected to said discharge circuit so as to produce a spark upon break down of the valve.

23. In an impulse ignition system for variable speed internal combustion engines, means driven by the engine for generating current impulses at a variable frequency determined by the speed of the engine, a non-capacitative impedance connected across the generating means, a condenser in parallel with the impedance, a discharge circuit for the condenser comprising an electric valve adapted to break down when the applied impulse attains a predetermined voltage, and an ignition device connected to said discharge circuit so as to produce a spark upon break down of the valve.

24. In the combination as defined in claim 23, said impedance consisting of a step-down transformer. f

25. In the combination as defined in claim 23, a step-up transformer having its primary in series with the condenser and valve, said igniting device being arranged in series with the 'secondary of said transformer.

DONALD W. RANDOLPH. RALPH H. MITCHEL. 

